Spark plug



May 5, 1925. '1,536,893

H. LEGGE-TT SPARK PLUG Filed May 28, 1923 liar-werf L egge';

" UNITED STA HERBERT LEGGETT, or KANSAS CrTYK, MISSOURI.

Patented May 5, `19215.

TESL

SPARK PLUG.

application med May 2s,

To all `cli/rom t may concern."

Be it known that I, HERBERT LEGGETT, `a

" citizen of the United States, residing at CFI . to prei gnite enter the spark plug.

Kansas City, in thel county of Jackson and State of Missouri, have invented certain new and useful `Improvements in f Spark Plugs, of which theifollowing. is a specification. f f ,y

My invention relates tospark plugs of the character employed in the ignition systems of internal combustion engines, and my primary object is to provide a durable device of this character which will not readily becomefouled with oil and the products of combustion, but on the contrary, will be practically self-cleaning and require but little attention after being installed in an envine.

attain the foregoing object by employ-` ing7 among other features, a new form of" electrode which is so shaped as to direct a stream of gases around the companion electrode with such velocity that oil andthe products of combustion cannot .readily lodge between said electrodes and cause a short-circuit of the ignition current.

Said new form of electrode is preferably constructed of metal, such, forexample, as

. nichrome, or Monel metal, which is capable of successfully withstanding high temperatures,` and is purposely vmade thin so that it will readily become heated with cath explosion to a sufficient degree to burn olf oil deposits, and yet not retain enough heat the successive combustible charges. x.

Said ew form of electrode also coacts with the shell ofthe spark plug in forming a trap for intercepting .a portion of the oil and products of combustion before they plug far enough to cause ignition trouble. p In orderthat the inventionmaybe fully understood, reference will now belhad to the accompanying drawing', in which: Fig. 1` is aside elevation of the spark( Fig. 2 is a vertical Section on line DLL-IIS of Fig. 1. f

Fig. 3 is a detail perspective View of a tubular electrode constituting an important feature of the invention; y

. Fig. 4 is a detail (perspective View of an annular spacing element employed in carryino' out the invention.y

tReferring now to the .various parts, 1

1923. Serial No. s41,916;`

'designates a metallic shell having external threads 2 at its lower end so that itr may be screwed into v the cylinder'head ofthe engine, not shown. y l V 3 designates an insulator made of any suitable material such as porcelain, mica, etc. Saidfinsulator may be secured withinv the shell 1in anypreferred or well-known manner. In tlm-drawing, Iv have shown it removably vheld in lposition by a bushing 4 threaded into the upper portion of the shell l, an asbestos or other suitable gasket 5 be ing placed about such insulator 3 to protect the same from being damaged when the shell 1, and K bushing 4 is screwed into the from expansion strains.'

A stem-like electrode 6, extends through the insulator 3 and is provided at its upper ythreaded end with the usual nuts 7 and 8 adapted to hold the terminal of a high tension lead wire of the usual ignition system, not shown. The lower portion ofthe'electrode 6 extends axially kthrough a tubularv electrode 9 preferably shaped somewhat on the order of a Venturi tube. The upper enlarged end of the tubular electrode 9 is providedwith a marginal flange 10, which is grounded on an annular shoulder 11 within the shell lfby an annular spacingelement 12 which is pressed downwardly upon the flange rv by the insulator 3 and the interposed gasket 5. The interior surface of the lower constricted portion 13 of the tubular electrode 9 is spaced from. the insulated elec-- trode 6 to leave an annular spark gap 14. .n

By 'constructing the tubular electrode 9 asshown and described, it is apparentthat when the combustible mixture is compressed ff 1n they combustionk chamber of the engine a portion will be forced into the chamber 15,

vformedby the tubular electrode 9, the spacingelement 12, and the lower portionof the insulator 3. Then, as such portion of the combustible mixture is exploded by the spark atthe gap 14,- the resultant high' pressure will cause the burnt gases to rush out through the restricted opening-13 of the `.tubular electrode 9 at such high velocity as to carrygoif carbonandy other products of combustion `which would otherwise tend to cause a short 'circuit between the electrodes 6 and 9. Itis alsoapparent that any products of combustion blow-n from the 'combustion chamber ofthe engine into the lower portion of the spark plug will be trapped in the chamber-'16, yformed by the. lower interior portion of the shell 1 and the exterior portion of the tubular electrode 9, and thus be prevented from collecting around the lower portion of the insulator and causing a short circuit between the electrode 6 and the shell l.

Oil is also prevented from becoming deposited in the restrictedgfopening 13 of the tubular electrode 9 by the stream of gases rushing through said opening, and :further`r by the relatively high temperature attained by the tubular electrode@ due to the heat generated by the explosion of the successive charges of the combustible mixture.

From the foregoing description it is apparent that I have produced a spark plug embodying the advantages above pointed out, and while I have shown and described the preferred construction, combination and arrangement of parts, I reserve the right to make such changes as properly tall within the spirit and scope of the claim.

Having thus described my invention, what I claim and desire to secure by Letters Patent, is:

In a spark plug, an outer shell, a stemlike electrode extending through and insulated from said shell, and a second electrode cooperatively associated with said irst elec trede, pendent from interior of outer shell, and consisting of two thin conical tubes joined at their reduced ends.

In testimony whereof I affix my signature. in the presence oftwo witnesses.

HERBERT LEGGETT.

Witnesses:

L. J. FISCHER, F. C. FISCHER. 

